The Role of Blood Culture Tests in Diagnosing Infections

Blood culture tests are vital diagnostic tools used to detect active or potential infections in the bloodstream. These diagnostic marvels play a vital role in uncovering hidden infections lurking within our bloodstream. By culturing a person's blood sample, these tests can identify the presence of bacteria, fungi, or other pathogens that cause bloodstream infections (sepsis). 

Timely and accurate detection of infections through blood culture is crucial, as it enables healthcare professionals to promptly provide treatment, reducing the risk of complications and potentially saving lives. Let’s take a look at what are blood culture tests.

What Is the Meaning of Blood Culture Test?

A blood culture is an examination aimed at identifying microbes (bacteria, viruses and fungi) in the bloodstream that are not visible to the naked eye. Upon detecting these microbes, the test serves the purpose of guiding doctors in selecting the most effective medications to combat the infection.

Healthcare providers may request a culture blood test when you display symptoms of infection possibly caused by bacteria or fungi. These tests also help in diagnosing and differentiating between diseases with overlapping signs and symptoms. Additionally, it may be conducted if an infection in a specific body area is suspected to have spread into the blood.

Signs & Symptoms of Blood Infection

A blood culture test is generally done to detect infections in the blood. A blood infection has the potential to impact various parts of your body, resulting in a wide range of symptoms.

For instance, if your condition is sparked by an infection in your blood, this can result in blood poisoning (septicaemia). This is caused by the entry of bacteria, fungi, and viruses into the bloodstream due to conditions like an infected tooth, pneumonia, or urinary tract infection among others. You might experience a sepsis rash on your skin. This rash manifests as red and discoloured patches, with small, dark-red spots visible on your skin.

Other common symptoms of a blood infection include:

• Generalised low energy
• Generalised shaking that may be accompanied by chills
• Fever (above 37.7° Celsius) or hypothermia (below 35° C) (extremely low body temperature)
• Warm or clammy or sweaty skin
• Increased or decreased urge to urinate
• Faster heart rate
• Low blood pressure
• Confusion or agitation
• Difficulty in breathing or rapid breathing (hyperventilation)
• Severe pain or discomfort

Tests that Detect and Diagnose Blood Infection in the Body

Several common lab tests for infection can be done for potential signs and symptoms of sepsis. Although none of these tests can independently diagnose sepsis, a combined analysis of their results alongside information about your medical condition and a physical examination can help your doctor reach a diagnosis. Let’s take a look at different tests for blood infection other than blood culture test:

• Complete blood count (CBC): It is a routine blood test that assesses the number of white blood cells in your bloodstream, red blood cells, platelets, and haemoglobin. White blood cells, or leukocytes, play a vital role in combating bacteria, viruses, and other harmful agents. Elevated levels of white blood cells may suggest an active infection, while low levels can indicate the risk for an infection.
• Monocyte distribution width (MDW): This test is a component of the CBC test that gauges the variability of monocytes, a type of white blood cell. An infection often leads to an increase in the variability of monocytes, which can be measured through MDW.
• C-reactive protein (CRP) test: It is synthesised by your body in response to inflammation, which can be caused by various conditions, including infections.
• Lactate test: Lactate, a by-product of organs when oxygen supply is inadequate, can arise from intense exercise, severe infection, heart failure, and other conditions. Elevated levels of lactic acid, resulting from an infection, serve as a significant indicator of sepsis.
• Prothrombin time and partial thromboplastin time (PT and PTT), d-dimer, and platelet count: These are essential blood culture tests that reveal the impact of sepsis on blood clotting within your body. High PT and PTT levels signal poor clotting, while low platelet counts indicate excessive unseen clotting in small vessels. Elevated d-dimer levels suggest large or numerous tiny clots, common in sepsis. 

What Is the Procedure for a Blood Culture Test?

The blood culture test does not require any special preparation needed in other tests. A blood sample will be withdrawn from you by tying a tourniquet around your arm. A tourniquet puts pressure on the blood vessel and allows for the veins to become more visible. The blood culture test time is short, and the technician will follow these steps during the blood culture test procedure: 

• The site from where blood needs to be drawn is cleaned using an antiseptic like chlorhexidine to prevent contamination by skin organisms. After this, the needle is used to draw the blood. This practice minimises the risk of false-positive results.
• The blood sample is sent to a laboratory and cultured in a specialised dish to monitor the growth of bacteria or disease-causing germs.
• A Gram stain (a technique to observe bacteria by using stain) may be suggested to identify bacteria using specific-coloured stains.
• Multiple blood cultures are often performed to increase the chances of detecting infections in the blood.

When the needle is inserted to draw blood, you may experience moderate pain or just a stinging or pricking sensation. After the blood draw, there might be a slight bruise at the site, which typically subsides quickly. The blood culture report time is usually several days.

How Would It Be If I Got Both Positive and Negative Blood Culture Test Results?

Your blood culture report will generally have the result listed as positive or negative for the specific microbes. A positive result indicates the presence of that specific bacteria or yeast in your blood, while a negative blood culture test means that no evidence of any bacteria or yeast was detected in the blood sample.

In some cases, you may receive blood culture test normal range (negative result) from one test and a positive result from another. This is known as abnormal results or false positives. This can occur due to possible contamination from bacteria present on the skin during sample collection or on lab equipment during testing.

Blood culture tests play a critical role in diagnosing infections by identifying pathogens in the bloodstream. When combined with clinical information, these tests aid healthcare professionals in providing appropriate treatments, leading to better health outcomes and improved infection management.

Book Lab Tests at Home With Orange Health Labs

You can follow these steps to book a lab test at home:

1. Log into our website. 
2. Submit your details. 
3. Our highly trained professionals will be at your doorstep for sample collection within a short time.

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